Unintelligibility refers to speech that is extremely difficult or impossible for listeners to understand. A person’s speech may be unintelligible due to numerous factors: severe articulation or phonological errors (e.g., numerous sound substitutions/omissions in children with a phonological disorder), motor speech disorders such as dysarthria (where imprecise articulation, voice, or prosody reduce clarity), or structural/anatomical issues like cleft palate. When speech is unintelligible, even familiar listeners struggle to discern words or meaning without context.
SLPs assess intelligibility both quantitatively (percent of words understood) and qualitatively (identifying error patterns contributing to breakdown). High unintelligibility can significantly impact a person’s academic, social, and vocational participation. Clinically, improving intelligibility is often a primary goal – therapy may target correct production of sounds (articulation therapy), use augmentative communication as a supplement, or teach strategies like slowing rate or using gestures to aid listener comprehension. The ultimate aim is to make the speaker’s intended message more accessible to listeners, thereby enhancing functional communication.
Coplan, J., & Gleason, J. R. (1988). Unclear speech: Recognition and significance of unintelligible speech in preschool children. Pediatrics, 82(3 Pt 2), 447–452. (Provides benchmarks for intelligibility—e.g., by age 4 speech should be fully understood.) PubMed: Link
Kent, R. D., Miolo, G. M., & Bloedel, S. B. (1994). The intelligibility of children’s speech: A review of evaluation measures. American Journal of Speech‑Language Pathology, 3(3), 81–95. Link
